This invention relates to electromagnetic switchgear. More particularly, this invention relates to electromagnetic switchgear having movable contacts mounted to a shiftable contact carrier for alternatingly engaging and disengaging respective stationary contacts.
As described in U.S. Pat. No. 3,334,319 to Herrmann, an electromagnetic switchgear includes contacts which are arranged so that the breaking of an engagement between a pair of contacts and the formation of an engagement between another pair of contacts do not occur simultaneously. Between the opening of one connection and the closing of an associated connection, the contact bridge carrier must traverse a preestablished distance. If, however, the first pair of contacts are welded to one another, one of the corresponding contact bridges may be deformed during motion of the contact bridge carrier with the possible result that the opening connection and the closing connection occur simultaneously. This eventuality cannot be avoided with the electromagnetic switchgear assembly disclosed in Herrmann inasmuch as the travel distance of the contact bridge carrier is necessarily restricted.
As disclosed in German Petty Patent (Gebrauchsmuster) No. 84 31 938 and in German Laid Open Application (Auslegeschrift) No. 11 97 535, an elastic coupling between a contact carrier and an armature is provided for adapting the movable magnet part to the fixed magnet part, the coupling spring being accordingly designed.
An object of the present invention is to provided an improved electromagnetic switchgear of the above-mentioned type.
Another, more particular, object of the present invention is to provide such a switchgear in which a closing connection between a pair of contact members is prevented in the event that another pair of contact members are welded to one another.